The IS-95 and CDMA2000 standards are focused on supporting wireless telephone call service in today's cellular systems. However, in contrast to wireless telephone calls which usually involve two participants, wireless dispatch (or group) calls can involve three or more call participants. In a dispatch call, one mobile station (MS) transmits (i.e., in talk mode) while the other members of the group receive (i.e., in listening mode) at any given time. When the MS with the transmit prerogative releases its “Push-to-talk” (PTT), a message is sent to its base station (BS), and the BS places the traffic channel in an “open mode.” While in this mode, any other MS can request a transmit prerogative by signaling a PTT. The BS allocates a transmit prerogative to the first arriving request. While this description is for a single-cell call, it can be applied to a multi-cell call with the addition of a central dispatch call controller, which arbitrates transmit prerogative requests instead of a controlling BS.
In a CDMA system such as that described in U.S. Pat. No. 6,519,239 (U.S. patent application Ser. No. 09/443,538), entitled “METHOD AND APPARATUS FOR PROVIDING DISPATCH SERVICE IN A CDMA COMMUNICATION SYSTEM,” group call voice frames are transmitted using standard CDMA traffic channel procedures except that a common long code is used instead of an individual long code computed from the MS's ESN. Thus, the MSs in the group call share a single forward-link traffic channel, while the transmitting MS transmits via the corresponding reverse-link traffic channel. However, in a prior art system where only the transmitting MS uses the reverse-link traffic channel, listening mode MSs are unable to participate in the signaling required to effect a handoff. Therefore, a need exists for an apparatus and method to provide handoff for listening participants of CDMA dispatch services.